Face detection is an age old process and is widely used in popular applications like Face ID by Apple, FaceApp, in surveillance cameras in China and many other applications. Today, we have sophisticated machine learning techniques which can perform face detection with near human precision and near real-time performace. What is interesting is that even in 2001, we had algorithms in use for Face detection. Yes, we are going back 2 decades. A time machine learning still was yet to blow up and Face detection's future was uncertain. Viola Jones algorithm is one which was used and which we have forgotten in light of stronger techniques.
This is a companion discussion topic for the original entry at http://iq.opengenus.org/face-detection-using-viola-jones-algorithm/